Electrostatic condenser



Jan. 19, 1932.

B. J. BUTLER ELECTROSTATIC CONDENSER Filed April 30, 1926 4 Sheets-Sheet 1 INVENTOR 5ENJAM/l/u/5UTLER Jan. 19, 1932. B. J. BUTLER 1,841,571

ELECTROSTATI C CONDENSER Filed April 30, 1926 4 Sheets-Sheet 2 INVENTOR BENJ/IM/IV J 5072. 51%

ATTORNEY Jan. 19, 1932. B. J. BUTLER 1,341,571

ELECTROSTATIC CONDENSER Filed April 50. 1926 4 Sheets-Sheet s i ATTORNEY Jan. 19, 1932. BUTLER 1,841,571

ELECTROSTATIC CONDENSER Filed April 50, 19 26 4 Sheets-Sheet 4 ATT/ORNEY Patented Jan. 19, 1932 UNITED STATES PATENT, orrlcs BENJAMIN J. BUTLER, O1 SOHEBVILLE, MASSACHUSETTS, ABSIGH'OB, BY IESNE A8- SIGNHENTS, '10 GENERAL ELEOTRIO COIPANY,.A CORPORATION OF NEW YORK I ELECTROSTATIC CONDENSER- Applicatlon filed April 30, 1926. Serial Io. 105,655.

This invention relates to electrostatic condensers, more particularly of the ty adapted for low-capacity, low-potentia service, particularly at high frequency as radio receiving condensers.

An object is such a condenser of the greatest practicable efiiciency and sturdiness and the lowest practical factory cost.

The invention consists of the construction, (method and product), substantially as shown in the drawings, which are approximately to scale, and of which Fig. -1 is an exploded elevation of a suitable condenser stack; r

Fig. 2 is a lan of an insulating stiffening plate (as of akelite duck) for application in duplicate to the two ends of the stack;

Fig. 3 an exploded elevation of an assembly of the stack of Fig. 1 and two plates like that of Fig. 2;

Fig. 4 a perspective of one of two' duplicate terminal-clips or U-clamps for the assembly of Fig. 3;

Fig. 5 a perspective of a metal connecting lug which may be held to the stack of Fig. 1 inside the clamp of Fig. 4;

Fig. 6 a perspective of an assembly of Figs. 1 and 2, wherein the oppositely projecting foil-bunches of opposite potential (alter- 1 nating foils in the stacks and projecting far beyond the sides of the stack Fi 1) are forced over and down upon one of t e stifleningplates IS;

ig. 7 a plan of an assembly of Figs. 46 prior to the secure clamping of the stack;

Fig. 8 is a section at 8-8.of Fig. .7

Fig. 9 a section of the condenser similar to Fig. 8, but in working relation to a clampproducing tool, in readiness for operation;

Fig. 10 a view like Fig. 9 but wherein the clamp-producing tool has been operated to effectuate the permanent clamping;

Fig. 11 a plan of the completed condenser resulting from the operation shown in Fig. 10;

Fig. 12 a perspective of a form having two sets of different forms of terminals, i. e., one set integral with the clamps and another set separate from the clamps;

Fig. 13 a perspective of a form having one set of terminals integral with the clamps, Fig. 14 being a section at 14-14 of Fig. 13; an

Figs. 15-18 showing a form having integral terminals similar to Figs. 13-14 but illustrating various features some shown in other figures but more clearly here and also area.

The invention hereof is an improvement on the condenser of the U. S. patents to Van Deventer, No. 1,181,623 of May 2, 1916 and to Hatch 1,574,424 of February 23, 1926; and the parts hereof which are similar to parts thereof are the stack S of Fig. 1, the partial assembly of Fig. 6 and the metal U-clam of Fig. 4 applied to the partial assembly of ig. 6 as shown in Fig. 7. That is, stack S, Fig. 1, consists of alternately laid sheets of dielectric M (as mica) and armatures such as lead foils F (sheets of copper, if few in number, to prevent tearing), such armaturesheets extending a considerable distance outside the stack so as to permit their being folded'over on top of one or both the two insulating stiffeners on the ends of the stacks as in said patents and two metal U-clamps or biped clips UC (Fig. 4) are slipped over opposite sides of the stacks (Fig. 7) so that their legs L engage the stack ends, clamping the stack and its sheets in intimate contact with one another, all as in the manner usual in said Van Deventer patent.

But in said patent, the U-clips are liable to slippage, and the present invention involves improved means and method of positively maintaining them permanently in position and in compressing relation with the stack, as well as other improvements now to be described.

As shown in Fig. 2, each insulatin stiffener IS is formed with perforations In Fig. 5 is shown one of the two sheet metal condenser terminals T, stifl but bendable, independent of clips U0, and having a flat portion perforated at H1 lying on the respective folded foil-bunches (Fig. 8) and held in good contact therewith by the U- clamps. Each independent terminal T has an outer end projecting outside the stack and thus having any desired configuration and construction, as the part in Fig. 5 with the oblong perforation 1, and in a plane at right angles to the flat portion perforated at H1, or with the part shown in Figs. 7, 8 and 11 in the same plane but at an angle with the fiat stack-part of the terminal, or with the various other terminail-constructions shown in the remaining Figures 1218. This independency of the terminals from the U- clips permits the latter to be made standard for all condensers irrespective of the type of terminal construction for different condensers. I

As shown in Fig. 7, the holes H2 in the 1,]- clips have the same diameter as the holes 1n the independent terminals; but the. holes 1n insualting stiifeners IS are conslderably lar er.

'Fhe two U clips UC contact with two terminal plates like T of Fig. 5 and are electrically spaced from one another midway of the length of the stack (Figs. result that insulating plates IS (of bakelite duck) are relied on to stiffen the stack, being for that purpose of substantial thlckness so that the holes H thru them (Fig. 2') have substantial depth. The insulating character of these plates IS acts to separate from one another the opposite potential foilbunches (F, F, Fig. 3), and independent terminals T, etc., whatever the specific construction of the terminals may be. )Vhen terminal plates T are used, the clip-clamps UC need not be in circuit.

As shown in Fig. 8, the holes are in central registry, between clips UC, (holes H2), terminals Tl (holes H1), and insulating stiffener IS (holes H), and said three types of parts are assembled (Fig. 8) prior to the extraordinary operation shown in Figs. 910, wherein the metal of the walls of holes H2 in the U-clips is cold-flowed or extruded into the larger holes H in insulating stiffener IS. (And similarly as to the walls of holes H1 in terminal plates used).

The apparatus of Figs. 9-10 comprises duplicate members D, Dl each having integral tapered hardened steel pins P spaced apart to enter the registering holes H, H1, H2 in the condenser structure. Flat surfaces FS of members D and D1 (Fig. 10) extend between and beyond pins P so as to act to compress the entire condenser in addition to the extruding action of the pins P.

Fig. 9 shows the pin-extruding action in process of operation, and Fig. 10 shows the over-all compressing action by which the 711), with the H T when such plates are hardened steel punch-pressingv metal clips are ermanently set in compressing relation to t e stack.

In Fig. 9 members D, D1 have been caused to move relatively toward but not to one another, as by the action of a suitable press forcing D1 downwardly. This results in the ends of pins P, smaller than their roots, entering in holes H2 in the metal U-clips. Such movement, continued, Fig. 9, results in the contact of the progressively thicker portions of pins P with the metal walls of holes H2, thereby progressively extruding the metal of said walls into the larger holes in insulating stiffener IS; and such metal drives before it the metal of the walls of independent terminals T1 and also the metal of the foil-bunches in the path of the points of pins P. This of course makes good contact between the independent terminals T1 and the respective foil-bunches. Also, as the upper and lower sets of pins other and their larger diameter-ed portions pass into the registering holes, the inwardly extruded metal portions are extruded radiallytoward the side walls of holes H in in sulating stiffener IS, so that, if said holes are small enough, as they preferably are, then the radially extruded metal is forced radially or laterally, at right angles to the direction of movements of pins P, into the yielding walls of the bakelite duck (bakelized linen) IS, especially at the end of the pin movement as indicated in Fig. 10. Bakelite duck is harder than the metal of the U- clamps, but is compressible. It is very strong mechanically and an excellent electrical insulator. In their action the parts are consolidated in permanently tight form and compensation is effected for any minor lack of registery of the holes of each series, i. e. H

H1, H2. The root or base of each pin P is much larger in diameter than holes H2 and H1 respectively in the U-clips and in the independent terminals T, but preferably is a little smaller than holes H in insulating stiffeners IS. Said stiifeners are of sufficient thickness, relative to the dimensions of the other parts, to prevent the extruded metals from extending to the faces of stack S or the foils F therein.

As shown in Figs. 9-10, the length of pins P is such that the complete metal-extrusion of my method is effected by the time that the points of the pins reach the end faces of stack S.

In the first part of the operation, which is shown in Fig. 9, the inner edges of legs L of the U-clips are liable to be turned outward (away from the end faces of the stack) by the extruding operation. But those clamp edges or ends are turned back and inward against the stack as soon as they are reached (Fig. 10) by the flat faces FS of punches D, D1 (Fig. 10).

The most important part of the operation,

P approach one an holes H and H2 (and preferabl however, whereby the final desired result is 10. This final action on the condenser of the final comparatively slight movement of D, D1 toward one another, deforms the U-clips and; puts the entire condenser under heavy compression, bringing the metal and foil sheets of stack S into intimate contact with one another, i. e., the condition desired for maintaining the capacity constant as lon as such contact-intimacy is maintained. nd such intimacy ,is in fact maintained here because, during such final over-all compressing action by punch-surfaces 'FS, pins P on D, D1 also are making their final movement toward one another, thereby "concluding their extruding action and placing the extruded metal permanently into position simultaneously with the final metal set which is imparted to clip-legs L by the final action of punch-faces FS; all whereby the parts are set and locked in their compressing relation. That is, as the entire structure is being compressed into its final state of compression, b

the final movements of punch-surfaces F the. movements of the sheets and plates of the structure in parallel planes toward one another, is closely followed up by the metal extruding action in and about the registering H1), so that at any desired state of fina compression, and wherever the relative movement of D and D1 toward one another ceases, the extruded metal of clips UC (and preferably also T) -is permanently set in position to maintain permanently such desired compression. The character of the metal of the U- clips and its thickness (ductile metal such as hard brass, mild steel or even copper not too hard) are such that it (and the metal of independent terminals T if used as preferred) will set permanently in any position to which it has been extruded. Altho reliance is placed on the thickness and kind of insulating material of plates IS to stiffen the stack between the two U-clips, yet for stack-clamping purposes, the metal U-clips are relied on. And for the purpose of distributing the clamping pressure with greater uniformity on the stack throughout the area of the metal clamps, I

prefer to provide a pair of complete sets of extrusions for each U-clamp as shown in Fig.

11, wherein XT indicates the exterior appearance after the completion of the extruding operation of Fig. 10. Fig. 14 shows the interior result of the extrusion of Figs. 9-10.

The over-all compression applied in Fig. preferably is so great that insulation IS may yield substantially (i. e., a useful yielding) altho actually but slightly. On that account and on account of the tendency of stack S to expand after being highly compressed, the entire completed structure inside the U-clips may have a tendency to expand outwardly against the clamps. For those reasons it is not disadvantageous but rather useful that the metal clamps have some springiness, as being cooperative with the permanent setting of the extruded metal and of the deformation of the clamps as a whole by the operation of Fig. 10, (bul ed at the base of th'e U) in maintaining t e desired stack-compression; altho it is difficult to observe in any given case, how the useful effect is proportioned between clamp-resiliency and clamp-set.

It is to be noted that, quite independently of the Fig. 10 stack-compressing, the stack previously has been put under considerable compression in the initial extruding operation of Fig. 9. And as above stated, in Fig. 10 the extruding action continues while the stack is being put under further and final compression. Thus both extruding and compressing actions are going on thruout the operation of both Figs. 9 and 10, so that it is difficult to distinguish the operations of these two figures save by the fact that Fig. 9 shows the initial stages of the movements of D and D1 toward the foil stages thereof. The important thing, however, is thatat least the final stage of the extrusion shall be after the ermanent clamping deformation of the U-chp; and it is permissible to conduct the extruding and compressing deformation operations of Figs. 9 10 independently of one another, the compressing-deformation being efi'ected first. That is, the punching tools may comprise pins P and clamping surfaces FS which operate quite successively, and surfaces FS first, so that first the entire condenser structure is subjected to the desired final compression and deformation (Fig. 10) without any extrusion, and then, while such compression is maintained by such surfaces FS, the pins P all are moved toward the condenser to cause the metal extrusion and permanently lock the parts in their compressed condition, the clamps D, D1 being then Withdrawn.

When the independent terminals T are'employed, as preferred and shown, the extrusion of the metal of the walls of their perforations Hl serves to hold them, (in addition to the U-clamps), in rigid relation with the stack, quite independently of clamping pressure on such terminals which by such extrusion are prevented from turning in the stack, altho independent of the U-clamps.

Preferably, (Figs. 25), the insulating stiffener and the U-clamps (and the independent terminals when used) are perforated prior to the extruding operation of Figs. 910, in order to facilitate the extrusion, and particularly to remove some metal from the U-clamps so that upon extrusion such metal will not extend sofar inwardly toward the stack S as to require extra thickness of the insulating stifieners in order to prevent the extruded metal from extruding to the stack. But if desired the extruding of Figs. 9-10 may be effected without such preliminary perforations of such parts. The armatures, particularly when of f01l s, Wlll not rerplire preliminary perforation 1n any case. n any case, after the metal extrusion, there will be perforations thru the foils and parts UC, IS and T; and it is far preferable that perforations H (Fig. 2) or at least sufficiently deep indentations, be formed reliminarily in parts IS prior to the extru mg operation, in order to provide conditions most favorable for the metal extrusion, i. e., little and preferably no resistance by IS to the extruding movements of the portions of metal.

Of course the armatures may extend coterminously with thestacked parts of the independent terminals so as to obtain maximum area of contact between them.

F or best resultsof extrusion I recommend the following dimensions. Preliminary holes H in U-clips (Fig. 2) to be one-sixteenth inch. Base of conical end of pin 1 (Fig. 9) to be seven-hundredths inch, the height of said cone to be one-sixty-fourth inch; and the pin to taper from the base of the cone to a maximum diameter of onetenth inch, such tapering permitting ready withdrawal of the pin after the completion of the extrusion operation and without disturbance of the extruded metal portions. In the extrusion operation, the original onesixteenth inch holes H2 in the U-clips become enlarged (Figs. 11 and 14) to the maximum diameter of the extruding pins. The distance from the points of pins P to the flat surfaces F S to be nine-one-hundredths inch. And not only are stiffening plates IS perforated at H (Fig. 2) .preliminary to the metal extrusion operation, but those holes are much larger (Fig. 8) than the holes H2 in the U- clips (Fig. 4) so as to provide for the minimum resistance to the cold-flow of extruding metal in Figs. 9-10.

Fig. 12 shows a'form wherein, for special classes of service, and in addition to terminalplates T2 independent of U-clamps UC,

'- there are two terminals UCT extending laterally beyond the condenser, but these additional terminals are formed integral with the respective U-clamps. The extrusion processing on this condenser is shown as substantially the same as that of the other figures, the exterior appearance after extrusion being indicated at XT.

Figs. 13-14 show a form locking any terminals independent of the U-clamps, the two terminals UCT being integral with the clamp UC. As shown in both figures the extrusion is as shown in the other figures, save that the portions of the foil-bunches which are folded over on top of IS, are in direct contact with U0, on account of the omission of independent terminals T2 of Fig. 12 and the provision of integral terminals UCT. Fig. 14 shows most clearly that a space preferably is left, along the line of the registering holes, between stack S and the inwardly extruded metal clamp-rotating and stack-compressing portions. This is shown also in Fig. 10, but not so clearly.

Figs. 1518 are clearer showings of some features elsewhere described, and show also how clamps US can be and properly are extended to cover the entire active area of stacks S; Figs. 15 and 17, perspective and plan, showing the side edges Z1 of both clamps UC projecting nearly to the edges of the insulating stifieners IS which in turn are substantially co-extensive with the mica sheets of stack S (Figs. 3 and 15)., so that clamps UC in Figs. 1518 are substantially co-extensive with those edges of the stackfoils F (Figs. 1) which are spaced inside from the edges of micas MQFigs. 1 and 3. Also in Figs. 1518 the ends of legs L of the two clips UC are fspaced close together at Z so as to cover as much as possible of the stack without bringing the clips (which here are terminals) in contact withone another. Also in Figs. 1518 the holes-and extrusions K1 are spaced further apartg than in the preceding figures, toward said extended side edges Z1, but are locatedc'loser together, than in the preceding figures,- toward the ends of the clamps adjacent one another at the space Z; all this being forthepurpose of distributing the clampingactions of the extrusions XT symmetrically over the extended areas of legs L of the U- clips and therefore symmetrically over the area of stack itself. The character of the metal of the U-clips between extrusions XT and between them and the edges of legs L, and the thickness of such metal, are such that the over-all deformation of the U-clip effected in Figs. 9-10 and the extrusions XT themselves, cooperate in putting stack S under compression thruout its active area and in maintaining such compression permanently.

Figs. 1518 show a simple form lacking any terminals independent of the U-clips, the terminals UCTl being integral thruout with the clips; Figs. 1516 showing this form prior to the operation of Figs. 910, and Figs. 1718 showing the result of such operations. Fig. 16, a section at 1616 of Fig. 15, looking in the direction of the arrows, clearly shows the fact that holes H in the bakelite duck pieces IS are substantially larger than the clip-holes H2, so that as shown in Figs. 17-18, the holes H2 readily can be enlarged, by pin P of Figs. 9-10,

without undue resistance by the hard resistance material of IS, and so that the extruded metal XT readily can be forced to a considerable distance toward altho short of 5 the stack S. In each of Figs. 1 6 and 18 the bent end of integral terminal UCTl apars in elevation beyond the section. Figs. 16 and 18 also illustrate the preferred form wherein plates IShave substantial thickness in this invention as distinguished from being merely one or a few sheets of thin mica. ig. 18 reproduces the appearance of an actual sawn section of a condenser processed according to the invention and illustrates the fact that. plates IS are more highly compressed at those parts of their outer surfaces which are at and near the rims of holes \Vhile it may be that stack S is more highly compressed at its portions centering around 20 extrusions XT, yet that is not objectionable because such compression is not excessive, but is advantageous because it contributes to sufficient compression over the rest of-the area of the stack. It is wellknown that a high degree of compression is necessary to maintain the desired stack-capacity which varies if such compression is not maintained.

As shown, and as preferred, each of plates IS is much thicker than clips U0 and each is even thicker than the entire stack S itself. This thickness of plates IS is in addition to the generally hard and comparatively stiff and inflexible character of the insulating material composing them. The result is, that in respect of transmitting compressing strain to stack S from the separate metal U-clips, the plates IS act as if they were of metal, save for the fact that they must and do insulate the U-clip opposite-potential terminals (Figs. 1518) from one another. And said substantial thickness of spacing plates IS permits corresponding depth of their" holes I-I thereby in turn permitting ample extent of metal-extrusion XT without the latter touching stack S or requiring any perforations of the stack such as are necessarilyzto be made as in other condensers wherein rivets thru the stacks are employed to clamp and hold the U-clips to the stack;

It is clear that an advantage of this invention over such latter condensers, in addition to the saving in punching perforations in the mica and foil sheets of the stack and to the saving in rivets, is that all the extent of the stack-foils and micas is usefully employed electro-statically, so that for a given desired capacity the area of the stack and the associated plates may be substantially smaller. The condenser of the. present invention gen- 60 erally follows the condenser of said Van Deventer patent, preferably including the unerforated stack thereof, and not at all relying for clamping compression u on studs,

rivets, bolts or the like extending t ru perforations in the stack. The perforations in position on spacing and stifiening plates IS alone are used in lieu of perforation thru stack S itself, to coo rate with the securing means which are t e metal extrusions XT, and the latter are formed or manufactured in the first instance when and after the U-clips of settable metal above have been assembledlin final lates IS on stack S, said extrusions, being ornied by cold-flow, setting automatically upon the connection of the extruding force. The thick plates IS with their holes or cavities H, are generally desirable to be used, irrespective of their insulating charact r, because in small-capacity condensers, the stack is so thin that holes or cavi ties in it could not be deep enough to permit the desired extent of metal-extrusion from the U-clip, regardless of the reduction in stack area by' perforation of the stack sheets.

I particularly point out and distinctly claim the part, improvement or combination which I claim as my invention or discovery, as follows 1. An electrostatic condenser comprising a stack of dielectric and armature sheets, a plate face to face with an end face of such stack; and a metal clamp embracing said stack and plate; said plate spacing apart said stack and clamp; and a portion of the metal of said clamp which faces said plate being extruded into said plate, and a separate terminal lead interposed between the end plate and clamp and held in firm electrical and me chanical engagement with the stack by said extended portions of the clamp.

2. An electrostatic condenser comprising a stack including an end plate, and a metal terminal plate connected with an armature of the stack and projecting outside the stack; and a metal clamp independent of said terminal plate but embracing said stack end plate and terminal plate; adjacent portions of said metal terminal plate and clamp being extruded into said end plate.

3. An electrostatic condenser comprising foil armatures of opposite polarity projecting laterally from the stack and folded back over the stack; an end plate of the stack; and two metal embracing clamps extending around the stack and the respective opposite potential foils; a portion of the metal of said clamp being extruded into said end plate, and a separate terminal lead interposed between said end plate and clamp and being formed with depressions into which the extruded portions of the clamp project in the form of open-ended tubular drawn walls.

4. The method of locking a metal clamp about the edge of a capacitor stack having an end plate provided with a perforation, which comprises extruding some of the clamp metal nto said end plate perforation and applying pressure over a substantial portion of one side of said clamp around the extruded portion to true the same, all in one operation. 9

as I

5. The method of locking a metal clamp about the edge of a capacitor stack having end plates each provided with a perforation,

which comprises simultaneously extruding 6 clamp metal into said end plate perforations to form open-ended tubular drawn walls and applying pressure over a substantial portion of opposite sides of said clamp around the extruded portions, all in one operation. In testimony whereof I hereunto aflix by signature.

BENJAMIN J. BUTLER. 

